MPLS TE technology collects link bandwidth information of the whole network via extended Interior Gateway Protocol (IGP), and calculates an end-to-end tunnel connection complying with several constraint conditions by Constrained Shortest Path First (CSPF) algorithm; for example, by designating bandwidth information, MPLS TE technology may calculate an end-to-end tunnel which meets the bandwidth requirement and the type of service (TOS) requirement, and perform bandwidth resource reservation at the nodes along the tunnel. In case of resource shortage, MPLS TE can preempt bandwidth resource of low-priority LSP tunnels, thus to meet the requirements of LSPs which need much bandwidth or of important users. Meanwhile, the Fast Re-Route (FRR) technology based on MPLS TE can provide protection by FRR link or node protection when an LSP tunnel fails or congestion occurs on a certain node in the network, thus achieving a disturbance switching in less than 50 ms.
It can be seen from the above description that MPLS TE technology is a true end-to-end Quality of Service (QOS) solution. MPLS TE technology has become an important solution for QOS and reliability problems and the like in IP technology, and it is being deployed widely.
At present, MPLS TE technology is deployed end to end, for example, an MPLS TE tunnel is deployed between any two PEs (Provider Edge devices) in a network. MPLS TE technology may be combined with Multi-Protocol Label Switching Virtual Private Network (MPLS VPN), etc., so as to achieve higher QOS and reliability guarantee.
When MPLS TE technology is combined with MPLS VPN, etc., an MPLS TE tunnel serves as an outer layer tunnel of MPLS VPN, and the MPLS TE tunnel is not a tunnel established by IGP, but a Label Switched Path (LSP) tunnel established by Label Distribution Protocol (LDP).